Installing a footbridge with a tailored erection solution combining rotation and lowering operations was the first of its kind in Hong Kong. We created local history with our clients and partners on this occasion.
Due to the dense urban area and difficult ground access, erecting the FB1 footbridge demanded to think outside the box to install the deck at height. The approach involved to proceed in stages, each being a challenge which Freyssinet overcame with comprehensive solutions for the scheme design and the detailed design of bridge erection works and installation.
The owner and the railway company considered the installation of the footbridge spanning the LRT as a risky operation, due to the railway and road traffic at ground level.
Hence, they required to reduce the duration of installation works and consequent period of track possession. The conventional construction method using crane and scaffolding was not an option. After reviewing the site constraints and cost effectiveness of various bridge erection schemes with the client and the main contractor, Freyssinet designed the solution best suited to the project’s configuration. While the bridge was primarily supported on falsework, the structure was temporarily connected to the rotation platform; temporary stay cables were installed and stressed, so that the structure’s weight could be transmitted to the turntable. The bridge was rotated by 180 degrees to the right place and lowered to its final position.
Such a proceeding minimized the impact to the train services, decreased the risk of human harm while boosting execution of the operation.
The design and planning stages were essential to ensure the smooth running of operations and effective sequencing since potential clashes may arise during the different construction phases. A 3D modelling software was employed for clash analysis, construction planning and modifications of the structural design / erection methods to achieve the most appropriate scheme.
The inventiveness of our teams also resided in the flexibility of the solution provided, which was considered right from the design phase of the system: enabling operators to possibly reverse the rotation/lowering operation and replace equipment or parts of it at any occasion and at any time.
Before starting the bridge rotation, FB1 was supported by the bolt joints and temporary stay cables of the rotation platform. The structure’s overall stability was contributed by the counterweight with a safety factor of about 1.9 for overturning resistance. Anti-uplift devices were also applied for additional protection. Due to the unequal arm balance, the counterweight was 4 times heavier than the bridge. Therefore, the total weight of the whole moving structures reached 2,000 tons.
The rotation was achieved by operating 4 sets of 80-ton hydraulic push/pull jacks, sliding shoes with anti-uplift devices and reaction blocks on the circular sliding rail of the turntable. Guiding systems were installed to direct the rotation and to provide uplift resistance to the structures. The sliding surface were made of the stainless-steel plates and polytetrafluoroethylene (PTFE) sheets. Combination of these two materials created a low friction environment for the operation. PTFE sheets’ condition was monitored both during and after the bridge rotation: should any damage be found in the PTFE sheets, the operation could be stopped at once and PTFE sheets instantly replaced.
Then, FB1 was connected at both ends to the Hebetec heavy lifting equipment which had been installed at the temporary steel structures. 8 sets of 140-ton capacity strand jacks and fittings were used. A computer-aided control system ensured synchronization of all strand jacks during lowering and data collection during the operation for real-time monitoring.
Complete design of the temporary metallic structures taking over the weight of the bridges and design of the operation systems were performed by our Technical Team, which had to face complex site constraints and numerous load cases.
Prior to the execution phase, sufficient material tests and equipment demonstrations, as well as off-site and on-site trial rotations had been carried out. We learnt from our findings and modified our works and sequences accordingly with our Partners.
Although the stringent time requirement was challenging, our Operations Team ultimately completed all the project’s stages in a safe and timely manner. We built trust with our client!
The second phase of the Yuen Long Station LTR project, erection of the vehicular bridge (VB), took place in October 2021. To reduce the modification works on the temporary steel structures, VB will be partially constructed such that its weight remains equal to FB1’s.
Hong Kong “Never Sleeps” benefits from an excellent infrastructure, and city-dwellers expect it to remain operational at all times.
Footbridges connecting new developments built on both sides of existing railways and roads have become a real challenge.
Everyone -including engineers- brainstormed to come up with all sorts of ideas, most looked like they came out of computer games.
Considering all site constraints and very short time frame entitled to defy gravity with heavy loads, the name of the “game” would easily become “Mission: Impossible X”.
However, this is the exact moment when Freyssinet Hong Kong teams convinced the Authorities and all stakeholders that they would “just do it”.
Execution of these operations look amazing, but you cannot imagine the amount of work required before D day.
Congratulations to the whole team -because this was indeed true teamwork! And we are very proud to be the reference in town for this type of works!
You have a question about our solutions or you already have a project in mind? Please fill out the form below and our teams will get back to you shortly.
